Sex Determination: More Complicated Than You Thought

Određivanje pola: Komplikovanije nego što ste mislili

Translator: Bedirhan Cinar

Prevodilac: Jelena Jaranović Lektor: Tatjana Jevdjic

(Muzika)

My wife is pregnant right now with our first child,

Moja supruga je trudna i očekujemo naše prvo dete.

and when people see her with her big baby bump,

Kada ljudi vide njen veliki stomak,

the first question people ask, almost without fail, is,

prvo pitanje koje postave, gotovo bez izuzetka je:

"Is it a boy or is it a girl?"

"Da li je dečak ili devojčica?"

Now, there are some assumptions behind that question

Postoje pretpostavke iza tog pitanja

that we take for granted

koje uzimamo zdravo za gotovo zbog poznavanja ljudske biologije.

because of our familiarity with our own human biology.

For human babies, we take it for granted that there's a 50/50 chance

Za ljudske bebe, podrazumevano je da su šanse 50%

of either answer, boy or girl.

da bude dečak ili devojčica.

But why is it that way?

Ali, zašto je tako?

Well, the answer depends on the sex determination system

Pa, odgovor zavisi od načina na koji se pol određuje,

that has evolved for our species.

a koji se razvio kod naše vrste.

You see, for most mammals,

Vidite, kod većine sisara,

the sex of a baby is determined genetically

pol bebe je određen genetski

with the XY chromosome system.

XY sistemom hromozoma.

Mammals have a pair of sex chromosomes,

Sisari imaju dva hromozoma koji određuju pol,

jedan se nasleđuje od mame, drugi od tate.

one passed down from mom, and one from dad.

A pair of X's gives us a girl,

Par X hromozoma daje devojčicu,

and an X and a Y together gives us a boy.

dok X i Y zajedno daju dečaka.

Kako žene imaju samo X hromozom u jajnim ćelijama,

Since females only have X's to pass on in their egg cells,

and males can give either an X or a Y in their sperm cells,

a muškarci mogu imati i X i Y u spermatozodima,

the sex is determined by the father

otac je taj koji određuje pol deteta

and the chance of producing a male or a female is 50/50.

i šanse da će biti dečak ili devojčica su 50/50.

This system has worked well for mammals,

Ovaj sistem funkcioniše kod sisara,

but throughout the tree of life, we can see other systems

ali kod drugih živih bića možemo sresti drugačije sisteme

that have worked just as well for other animals.

koji funkcionišu dobro kod njih.

There are other groups of animals that also have genetic sex determination,

Postoje i grupe životinja koje imaju genetsko određivanje pola,

but their systems can be pretty different from ours.

ali njihov sistem se može znatno razlikovati od našeg.

Ptice i neki reptili imaju genetsko određivanje pola,

Birds and some reptiles have their sex genetically determined,

but instead of the sex being determined by dad,

ali umesto da pol određuje tata,

their sex is determined by mom.

to radi mama.

In those groups, a pair of Z sex chromosomes

Kod ovih životinja, mužjak stvara par Z hromozoma,

produces a male, so these males only have Z's to give.

pa mužjaci mogu dati samo Z hromozom.

However, in these animals, one Z and one W chromosome together,

Kako god, kod ovih životinja,

jedan Z i jedan W hromozom zajedno,

as a pair, produces a female.

kao par, daju ženku.

In this system, the chance of a male or a female is still 50/50,

Po ovom sistemu, šanse za mužjaka ili ženku su i dalje 50/50,

it just depends on whether mom puts a Z or a W

samo što od mame zavisi da li će dati jajnu ćeliju

into her egg.

sa Z ili W hromozomom.

Certain groups have taken genetic sex determination

Neke grupe imaju genetsko određivanje pola

in completely other directions.

koje funkcioniše sasvim drugačije.

Ants, for example, have one of the most interesting systems

Na primer, mravi imaju jedan od najzanimljivijih sistema

for determining sex, and because of it, if you are a male ant,

za određivanje pola, zbog koga, ako ste mužjak mrav,

you do not have a father.

vi nemate oca.

In an ant colony, there are dramatic divisions of labor.

U koloniji mrava postoji striktna podela rada.

There are soldiers that defend the colony,

Postoje vojnici koji brane koloniju,

there are workers that collect food, clean the nest and care for the young,

radnici koji sakupljaju hranu, čiste mravinjak i brinu o mladima,

and there's a queen and a small group of male reproductives.

a tu je i kraljica sa malom grupom mužjaka za parenje.

Now, the queen will mate and then store sperm from the males.

Kraljica će se pariti i sačuvati spermu mužjaka.

And this is where the system gets really interesting.

I ovde postaje stvarno interesantno.

If the queen uses the stored sperm to fertilize an egg,

Ako kraljica upotrebi tu spermu da oplodi jaje,

then that egg will grow up to become female.

iz tog jajeta će se izleći ženka.

However, if she lays an egg without fertilizing it,

Ali, ako ne oplodi jaje,

then that egg will still grow up to be an ant,

iz njega će se i dalje izleći mrav,

but it will always be a male.

ali će uvek biti mužjak.

So you see, it's impossible for male ants to have fathers.

Dakle, muški mravi ne mogu imati oca.

And male ants live their life like this, with only one copy of every gene,

I mužjaci mrava žive tako,

sa samo jednom kopijom svakog gena,

much like a walking sex cell.

skoro kao šetajuća polna ćelija.

This system is called a haplodiploid system,

Ovaj sistem razmnožavanja zove se partenogeneza

and we see it not only in ants,

i srećemo ga ne samo kod mrava,

but also in other highly social insects like bees and wasps.

već i kod drugih visoko društvenih životinja poput pčela i osa.

Since our own sex is determined by genes,

Pošto je naš pol genetski određen,

and we do know of these other animals that have their sex determined by genes,

a znamo i da se kod drugih životinja pol određuje genetski,

it's easy to assume that for all animals

lako je zaključiti da za sve životinje važi

the sex of their babies still must be determined by genetics.

da je pol bebe određen genetski.

However, for some animals, the question of whether it will be a boy or a girl

Ipak, za neke životinje, pitanje pola

has nothing to do with genes at all,

nema nikakve veze sa genima

and it can depend on something like the weather.

i može zavisiti, na primer, od vremena.

To važi za aligatore i većinu kornjača.

These are animals like alligators and most turtles.

In these animals, the sex of an embryo in a developing egg

Kod ovih životinja, pol zametka u jajetu

is determined by the temperature.

je određen spoljnom temperaturom.

Kod ovih vrsta, pol bebe nije određen onda kada se jaje položi,

In these species, the sex of the baby

is not yet determined when the egg is laid,

and it remains undetermined until sometime in the middle

i ostaje neodređen do nekog trenutka na sredini

of the overall development period, when a critical time is reached.

razvojnog perioda, kada se dosegne kritično vreme.

And during this time, the sex is completely determined

Tokom tog perioda, pol se potpuno određuje

by temperature in the nest.

temperaturom u gnezdu.

In painted turtles, for example,

Kod šarenih kornjača, na primer,

warm temperatures above the critical temperature

temperatura iznad neke kritične tačke

will produce females within the eggs,

će stvoriti ženke unutar jaja,

and cool temperatures will produce a male.

a hladnija temperatura će stvoriti mužjake.

Ne znam ko je smislio ovu tehniku pamćenja,

I'm not sure who came up with this mnemonic,

but you can remember that when it comes to painted turtles,

ali barem kada su kornjače u pitanju možete zapamtiti

they are all hot chicks and cool dudes.

da su one sve vruće cice i kul baje.

Za neke tropske ribe, pitanje pola

For some tropical fish, the question of will it be a boy or will it be a girl

isn't settled until even later in life.

rešava se tek kasnije u životu.

You see, clownfish all start out their lives as males,

Recimo, svaka riba-klovn je na početku mužjak.

Ali, kako odrastaju, postaju ženke.

However, as they mature, they become female.

They also spend their lives in small groups with a strict dominance hierarchy

One takođe provode život u malim grupama sa strogom hijerarhijom

where only the most dominant male and female reproduce.

gde se samo najdominantniji mužjak i ženka razmnožavaju.

And amazingly, if the dominant female in the group dies,

Zanimljivo, ako dominantna ženka u grupi ugine,

the largest and most dominant male will then quickly become female

najveći mužjak će vrlo brzo da se pretvori u ženku

and take her place, and all of the other males

i zauzme njeno mesto,

a ostali mužjaci će se pomeriti za po jedno mesto u hijerarhiji.

will move up one rank in the hierarchy.

Kod jedne druge okeanske životinje,

In another very different ocean animal,

the green spoonworm,

zelenog crva,

the sex of the babies is determined

pol određuje potpuno drugačiji aspekt okruženja.

by a completely different aspect of the environment.

Za ovu vrstu, pitanje je gde će larva

For this species, it is simply a matter of where a larva

happens to randomly fall on the sea floor.

pasti na morsko dno.

If a larva lands on the open sea floor, then it will become a female.

Ako se larva spusti na dno

iz nje će postati ženka.

But if it lands on top of a female, then it will become a male.

Ali ako se larva spusti na vrh ženke,

onda postaje mužjak.

So for some species, the question of boy or girl

Dakle, za neke vrste pol se određuje genetski,

is answered by genetics.

For others, it's answered by the environment.

dok za druge, na to utiče okruženje.

And for others still, they don't even bother with the question at all.

A, postoje i oni kojima je ovo potpuno nebitno.

Take whiptail lizards, for example.

Na primer, postoji vrsta guštera

For those desert lizards, the answer is easy.

koja živi u pustinji i za njih je odgovor jednostavan.

Biće ženka. Uvek je ženka.

It's a girl. It's always a girl.

They are a nearly all-female species, and although they still lay eggs,

Cela vrsta se sastoji gotovo samo od ženki,

i kada polože jaja, iz njih se izlegu njihovi ženski klonovi.

these eggs hatch out female clones of themselves.

So will it be a girl or will it be a boy?

Dakle, hoće li biti dečak ili devojčica?

Throughout the entire animal kingdom,

U celom životinjskom carstvu,

it does really all depend on the system of sex determination.

sve zavisi od načina određivanja pola.

For humans, that system is a genetic XY system.

Za ljude, to je genetski XY sistem.

And for me and my wife, we found out

A, što se mene i moje supruge tiče,

it's going to be a baby boy.

saznali smo - biće dečak.

(Kiss)